British light heavyweight Buatsi made a winning yet disappointing debut to his career under new promoters with a decision win over Zach Parker in the Manchester arena.
The Olympic bronze medallist's work rate appeared to earn him a judges' verdict in a tight 10-round fight at the boxing arena.
But the challenger found success, landing some telling clean blows in a contest where the techniques failed to mesh, with frequent clinching spoiling the fight.
The scoring judges judged it 96-94 to Buatsi, with the third a 95-95 draw.
"It wasn't my best display but what defines champions? They succeed," Buatsi said in the arena as he was greeted with disapproval from the crowd.
The British fighter returned to winning ways after his maiden career setback - an thrilling contest with Callum Smith in last winter - to secure a twentieth professional win.
Some ringside observers believed the challenger, 31, deserved the victory but the contender suffered the second loss of his 28-fight career.
Buatsi Earns Triumph in Uneventful Affair
The fighter's advancement has plateaued in recent years through promotional disputes and extended periods of inactivity.
Once tipped as the next star of UK boxing, he now stands trying to achieve expectations - maybe in what appears to be a last chance - under recent support.
He started carefully, with both competitors willing to overcommit in a tentative early stages.
Parker, whose only previous defeat came at super middleweight against John Ryder in 2022 after breaking his hand mid-fight, was making just his second fight at light-heavyweight.
By the middle rounds, Parker had stayed in contention, making life awkward for the favorite, who utilized a tight guard to barely take the more effective stanzas.
The audience's tolerance decreased amid constant clinching, with Parker slipping to the canvas several times during grappling.
Parker closed well, but multiple periods were challenging to assess. However, former world champion the boxing analyst - commentating on the broadcast network - had it significantly in favor for Parker, awarding Buatsi just only one stanza.
Buatsi progresses, but with the likes of hard hitter David Benavidez, and Russian champion Bivol leading the category, the path to championship success - on this evidence - still seems difficult.
Hatton Memorial Inspires All-Manchester Battle
In the supporting bout, Lyndon Arthur overcame Bradley Rea by split-decision in a terrific all-Manchester fight to capture the European light-heavyweight belt.
The venue became quiet for a profoundly moving memorial before the fight as 10 bells tolled in remembrance of local hero Ricky Hatton, who died at age 46 in September.
It was the first major televised match card in the location since the passing of Hatton. As the final chime ended, the silence became a chant of "there's just one Ricky Hatton".
The action inside the ropes equaled the emotion. Arthur was knocked down by a significant blow squarely on the jaw in the initial stage, standing uncertainly to his position on the count of eight.
But the red-colored attire of Arthur soon came forward again. On the opposite side, the opponent - in rival City blue - was injured early, noticeable damage appearing under his orbital area as the fighters traded hard punches.
The challenger, twenty-seven, delivered effective strikes but the champion, thirty-four, responded in kind with effective uppercuts as the action rarely dropped over twelve rounds.
The victor barely secured the verdict with official scores of even score, close margin and wider gap, but each competitor were persistent and brave, all the qualities their inspiration the legend represented.
